Ethylbenzene is a key raw material in the production of styrene and is produced by the reaction of ethylene and benzene in the presence of an acidic alkylation or transalkylation catalyst. Ethylbenzene production plants built before 1980 used AlCl3 or BF3 as the acidic alkylation or transalkylation catalyst. Plants built after 1980 have in general used zeolite-based acidic catalysts as the alkylation and/or transalkylation catalysts.
Liquid phase ethylation of benzene using a catalyst comprising zeolite beta is disclosed in U.S. Pat. No. 4,891,458 and European Patent Publication Nos. 0432814 and 0629549. More recently it has been disclosed that MCM-22 and its structural analogues have utility in these alkylation/transalkylation reactions, for example, U.S. Pat. No. 4,992,606 (MCM-22), U.S. Pat. No. 5,258,565 (MCM-36), U.S. Pat. No. 5,371,310 (MCM-49), U.S. Pat. No. 5,453,554 (MCM-56), U.S. Pat. No. 5,149,894 (SSZ-25); U.S. Pat. No. 6,077,498 (ITQ-1); International Patent Publication Nos. WO97/17290 and WO01/21562 (ITQ-2).
In the prior art alkylation/transalkylation processes, the desired monoalkylated compound is produced along with polyalkylated impurities by contacting an alkylatable aromatic compound and an alkylating agent in the presence of a catalyst. During the alkylation/transalkylation processes, the catalyst ages due to the deposition of coke and other deleterious materials on the catalyst. Such catalyst aging causes a decrease in the catalyst's activity for the conversion of reactants to products. To restore a catalyst's activity, the catalyst is often regenerated by controlled oxidation in air, or by other means. Following regeneration, the catalyst's activity is restored to a certain degree. However, the regenerated catalyst often has a reduced selectivity to produce the desired monoalkylated compound, and increased amounts of the more undesirable polyalkylated impurities are produced. Therefore, there is a need for improved alkylation and/or transalkylation processes that increase and/or control the activity and selectivity of such catalysts to produce the desired monoalkylated aromatic compound in a reaction zone. This invention meets this and other needs.